When astronauts enter space, they are exposed to weightlessness. Physiological and psychological challenges are waiting ahead. They may have a puffy face and experience space motion sickness, cardiovascular deconditioning, muscle atrophy, and bone loss.

Moreover, long-term spaceflight has been shown to result in 83% of astronauts with post-flight orthostatic intolerance. For such problems, exercise countermeasures can be the primary approach to resolve these changes. Head-down bed rest (HDBR) simulates physiological effects in weightlessness and is widely used in countermeasure testing, and efficacy of exercise interventions has been widely studied in HDBR with different periods as well.

Usually, the long-term bed rest experiment is completed in stages, and a positive control of separated exercise countermeasures rarely tests at the same time in these experiments.

The Chang'e-6/7/8 exploration mission has been announced officially by China recently, and the international lunar and Mars research station plans will be carried out within the 2030s. It can be predicted that China's future lunar and Mars surface exploration activities will last longer, have a larger exploration range, and have a more complex terrain to traverse and explore, which will pose severe challenges to the working performance of the planet rover and its adaptability to the planet surface environment.

One of the key problems will be to study the relationship between the mechanical properties of planet soil and the traction performance of the planet rover's wheels. The mixed terrains of terramechanics research are mainly composed of static stones and loose soil.

Whereas, the movement behavior of stones is often ignored while analyzing the influence of the wheel's traction performance caused by mixed terrain.